China will work for S.China Sea peace: Xi

China will work with Southeast Asian countries to safeguard peace in the South China Sea, President Xi Jinping has told Philippine President Rodrigo Duterte, who pledged to handle issues with Beijing in those waters bilaterally.

China claims almost the entire strategic waterway through which about $US3 trillion ($A4.2 trillion) worth of goods pass every year, building and militarising artificial islands. Brunei, Malaysia, the Philippines, Taiwan and Vietnam also have conflicting claims there.

"China will continue to work with ASEAN countries to safeguard peace, stability and prosperity of the South China Sea region," China's official Xinhua news agency cited Xi as saying to Duterte on Saturday.

Since coming to office 16 months ago, the firebrand leader has been conciliatory to Beijing, despite a ruling by an international arbitration court favouring the Philippines in its territorial dispute with China.

In the past, Duterte has repeatedly said he will raise the sea dispute at the proper time and avoided the issue when Manila hosted two regional meetings this year.

The United States has criticised China's construction of islands and its build-up of military facilities in the sea, and is concerned they could be used to restrict free nautical movement.